The present invention relates to a method of operating a drive device for a motor vehicle, and corresponding drive device.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
The drive device serves to power the motor vehicle, i.e. to provide an appropriate level of torque to power the motor vehicle. The drive device includes an internal combustion engine by which the necessary torque either by itself or together with at least one further drive unit is produced. The internal combustion engine can be operatively connected with at least one of the wheels of the motor vehicle, especially with a wheel axle of the motor vehicle. This is the function of the clutch.
The term “clutch” is to be understood as relating to any element having at least two states, whereby in one of the states there is an operative connection between the internal combustion engine and the wheel of the vehicle and in the other state the internal combustion engine and the wheel are disconnected from each other. In other words, the clutch is a releasable clutch, particularly a releasable frictional clutch. The clutch can, for example, be a starting element, such as an starting clutch, a clutch torque converter, in particular a hydrodynamic clutch torque converter, or the like.
When the clutch is disengaged, the operative connection between the internal combustion engine and the wheel is severed. However, when the clutch is at least partially engaged, torque from the internal combustion engine is transmitted to the wheel. When the clutch is fully engaged, the operative connection between the internal combustion engine and the wheel is rigid or substantially rigid. When the clutch is fully engaged, there is ideally no clutch slip between the internal combustion engine and the wheel.
In order to start the internal combustion engine, it is necessary to crank it to a minimum starting speed. This is realized by an electrical machine which, for example, is configured as a starter or as a starter generator. The electric machine can be permanently operatively connected to the internal combustion engine, particularly by a freewheel or overrunning clutch, so that torque supplied by the electric machine is applied to the internal combustion engine to start it, However, cranking of the running internal combustion engine does not carry along the electric machine.
It would be desirable and advantageous to provide an improved method of operating a drive device for a motor vehicle to obviate prior art shortcomings and to realize an efficient and fuel-saving operation of the drive device or internal combustion engine.